Vacuum may be used in vehicles to operate or to assist in the operation of vehicle brakes, ventilation systems, and other actuator devices. However, for engines that are boosted and that have relatively small displacement, it may be difficult to supply vacuum to all vacuum consumers (e.g., vacuum operated actuators such as turbocharger waste gate actuators, vehicle ventilation controls, and brake boosters) of the vehicle. For example, if an engine is operating at boosted conditions for a period of time, and at the same time vacuum is being consumed by vacuum consumers, the amount of vacuum in the vacuum system may be reduced to an extent that operation of one or more vacuum operated actuators may be degraded.
The inventors herein have recognized the above-mentioned disadvantages and have developed a vacuum prioritization method for a vehicle, comprising: providing vacuum via at least one vehicle vacuum source solely to a first actuator group when a pressure of a first vacuum reservoir is greater than a first threshold pressure; and providing vacuum via the at least one vehicle vacuum source to the first actuator group and a second actuator group when the pressure of the first vacuum reservoir is less than the first threshold pressure.
Operation of a vacuum system comprised of a plurality of vacuum consumers can be improved by prioritizing the use of vacuum between the various vacuum consumers. For example, assisting an operator to apply vehicle brakes via a brake booster may have higher vacuum use priority over operating a vehicle ventilation system. By making vacuum available to higher priority vacuum consumers and limiting vacuum available to lower priority vacuum consumers, higher priority vacuum consumers may operate for longer time periods when sources for producing vacuum may be limited. Further, the vacuum production capacity of vacuum sources may be applied solely to higher priority vacuum consumers rather than all vacuum consumers. In this way, operation of higher priority vacuum operated actuators may be improved.
The present description may provide several advantages. In particular, the approach may allow higher priority vacuum operated actuators to operate for longer periods of time when vacuum is not being generated by an engine of a vehicle. Further, the approach may improve the utility of vacuum produced during times of low vacuum availability. Further still, the approach can also limit the use of vacuum between secondary vacuum consumers so as to conserve vacuum between lower priority vacuum consumers.
The above advantages and other advantages, and features of the present description will be readily apparent from the following Detailed Description when taken alone or in connection with the accompanying drawings.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.